Assessing the potential of fast amplitude modulation pulses for improving triple-quantum magic angle spinning NMR spectra of half-integer quadrupolar nuclei

resumo

A comprehensive experimental and numerical study of the potential of fast amplitude (FAM) irradiation for improving the triple-quantum (3Q) magic angle spinning (MAS) NMR spectra of half-integer I>1/2 nuclei (Na-23, Al-27, Sc-45, Nb-93) was carried out. Materials of academic and industrial importance, such as infrared-emitter Na3YSi3O9, microporous aluminophosphate VPI-5, mineral andalusite, calcined kaolinite, Sc2O3 and relaxor ferroelectric PMN, were investigated. It was found that FAM pulses are indeed of practical relevance and particularly useful for the observation of the NMR resonances given by nuclei in distorted local environments (large quadrupole coupling constants). In addition, a novel strategy for the optimization of the FAM-II MQ MAS NMR experiment, which improves the multiple- to single-quantum coherence transfer efficiency, is also reported. Copyright (C) 2003 John Wiley Sons, Ltd.

palavras-chave

DOUBLE FREQUENCY SWEEPS; MAS NMR; MQMAS NMR; CROSS-POLARIZATION; MAGNETIC-RESONANCE; SINGLE-QUANTUM; I=3/2 NUCLEI; SENSITIVITY ENHANCEMENT; SIGNAL ENHANCEMENT; IONIC-CONDUCTIVITY

categoria

Chemistry; Spectroscopy

autores

Morais, CM; Lopes, M; Fernandez, C; Rocha, J

nossos autores

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